In Long Term Evolution (LTE) standardized by 3rd Generation Partnership Project (3GPP), N OFDM symbols from the head of each subframe are reserved for an area usable as a physical downlink control channel (PDCCH). The N value is called a control format indicator (CFI), and a base station (eNB) notifies a mobile station (UE) of the CFI value on a physical control format indicator channel (PCFICH) (e.g., Non-patent document 1).
The N value can be changed among subframes. Thus, a large N value can be set for a mobile station reporting a low channel quality indicator (CQI) value and therefore requiring many PDCCH resources, such as one located on the edge of a cell. Meanwhile, a small N value can be set for a mobile station requiring only few PDCCH sources, such as one located near the base station.